Interpretive Summary: Genetic resistance is the most effective way to control corn viruses, and sources of resistance have been identified in certain corn lines. However, the sequences of genes responsible for conferring resistance in resistant corn remains unknown. In order to better understand the different responses of resistant and susceptible corn, we took a next-generation sequencing approach to compare two resistant and one susceptible corn lines for response to Maize dwarf mosaic virus, a common corn virus. Our results showed that different genes were regulated in each corn line, and showed some of the sequences differences between the resistant and susceptible lines. These data begin to show plant pathways and sequences that might contribute to resistance to corn viruses.

Technical Abstract:
Maize resistance to viruses has been well-characterized at the genetic level, and loci responsible for resistance to potyviruses including Maize dwarf mosaic virus (MDMV), Sugarcane mosaic virus (SCMV), Sorghum mosaic virus (SrMV), and Johnsongrass mosaic virus (JGMV), have been mapped in several genotypes1. Although potyvirus resistance loci have been indentified, they are often hundreds of megabases and contain thousands of genes that could be candidates for controlling the resistance. Map-based cloning approaches have been attempted to isolate the genes responsible for conferring potyvirus resistance, but have not yet been fully successful2. Moreover, how the resistance genes trigger downstream molecular and biochemical mechanisms to confer resistance is not well understood. MDMV–infected plants develop chlorotic spots and streaks in darker green ‘healthy’ leaf tissue that progress into mosaic symptoms (Fig. 1). Susceptible lines and hybrids develop dwarfing symptoms and often have significant yield reduction. Host resistance to infection has been used to control MDMV in the U.S. for the past thirty years. The maize inbred lines Pa405 (U.S.) and Oh1VI (Virgin Islands) are highly resistant to infection by MDMV and other potyviruses, whereas Oh28 (U.S.) and B73 are susceptible. MDMV resistance is controlled by a single dominant gene, Mdm1, on chromosome 6, with genetic modifiers on chromosomes 3 and 10 also contributing3,4. In this study, we used next generation sequencing of maize transcripts on an Illumina platform to identify transcripts associated with MDMV resistance by: 1) characterizing the transcriptome response to MDMV inoculation; 2) identifying SNP between resistant and susceptible lines in transcripts that map to resistance loci; and 3) identifying transcripts present only in resistant lines.